The consumption of strawberries is generally restricted to seasonal availability, due to short shelf life, fast ripening and/or poor capacity to stand storage. Out of season, the market turns to frozen or chilled fruits, and preserved versions, with poor organoleptic properties. There is therefore, an unsatisfied need in the market for high quality canned strawberry.
U.S. Pat. No. 5,164,212 describes a method to color cherries using cochineal, multivalent metal ions and acid. The cherries are infused with a mixture of calcium ions, other multivalent metal ions, and cochineal dye at a pH at which the dye is in soluble form. The cherries are then infused with an acidification solution which results in the precipitation of an insoluble carmine-metal ion complex within the cherries. Here, the cherries must be cut in halves so the pulp can be exposed to the different process solutions. The description of the preferred embodiments in the patent also recommends a heating process to fix the color, at temperatures as high as 210° F. for times as long as five hours, which is suitable for cherries which have a high intrinsic firmness.
U.S. Pat. No. 5,310,567 describes a single step method which involves the direct addition of natural or artificial dyes into the can. The method comprises the steps of removing the cuticle layer of unripe strawberries, charging the strawberries in a container together with a dyeing solution containing the dyeing agent (cochineal and/or lac), degassing the contents of the container, then sealing the container and heating the sealed container.